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Need advice on test results and pool issue

I bought a house with a pool in AZ when I moved here 1 year ago. The pool was emptied/cleaned/refilled at that time. The water has had near perfect readings until about a month ago when I started seeing black/green staining on the pool walls. It didn't look like Algae spots, but more like a stain that continually grew as time passed. I am still not 100% sure what it is or if there is a way to tell for sure.

Anyway I started attacking it as if it were Algae and that is when the problems started. I used the algae killer from the pool store and started shocking with the Calcium Hypo and scrubbing the stains...There was some decrease it seemed in the staining, but it never went away completely. Then I started noticing that my chemistry readings began to fluctuate. The PH went up and the pull was acidic and I had a 7-1 TC/FC reading (6 CC).

After treating this with Soda Ash to bring PH down I continued to shock to get rid of CC and I accomplished that. The only problem is that now both TC and FC barely register at all. Now my PH has dropped and Alkalinity as well. Also, it looks like because of the shocking that my CH has gone way up. Here are the current readings.

FC - 0
TC - 1
PH - 6.8
ALK - 6
CYA - 50
CH - 1000

Of course I was taking direction from the pool store in everything I did. Now after reading these forums that was probably not a good idea. Besides now having to draing the pool (Something I shouldn't have to do since the water is less then a year old but probably related to the shocking). What is the best course of action going forward? The pool is clear, and besides the staining looks ok.

Re: Need advice on test results and pool issue

Cal-hypo is about the last thing you want to use in your pool given the high calcium levels we tend to start with.

Are those results from you own test kit? If not, order one of the ones listed in the link in my signature.

While draining water to lower the CH might be tempting, it may not be required and may not help as much as you might think. You should test your fill water for pH, TA, FC, CH to see what you are starting with.

If you keep a tight control on the pH you should be able to live with the high CH.

If you do not want to drain, then you need to raise your pH up to about 7.2. And then start the shock PROCESS (read Pool School) using liquid chlorine. Follow the directions exactly. Let us know if other questions come up.

Re: Need advice on test results and pool issue

My fill water PH is around 7.5 and CH is pretty high out here in AZ (400-450). Looks like I have added to that a bit with the Cal Hypo but maybe that isn't as big of an issue out here since it is high to beging with. I would rather not drain the pool if I can live with it for now. If not for this green/black staining in the pool I wouldn't even be able to tell there was a problem without reading the water tests. PH was holding at 7.2 until recently when it dropped to 6.8

Re: Need advice on test results and pool issue

So according to the pool calculator I should do the following in this order

Raise PH by adding 33oz of Soda Ash (Or 66oz of Borax).
Raise alkalinity by adding 56oz of baking soda
Shock pool by dumping in a full bottle (128oz) of bleach at 6% (Standard bleach from grocery store)

From what I read I should add the soda ash and BS first to get the PH and Alkalinity up, then shock the pool once that happens. In the meantime while I am waiting for PH to rise what should I do about chlorine?

Re: Need advice on test results and pool issue

You can add bleach while adjusting TA and pH ... just realize the pH test is not accurate when the FC is > 10ppm.

Also when you get to the shock process ... review the instructions as what you wrote above is not fully correct ... you have to keep testing and maintain the FC at shock level ... not just raise it once.

Re: Need advice on test results and pool issue

Thanks for the help...So for shocking...If shock value is 20 and 1 bottle of chlorine gets me there then I dump the bottle in every couple hours until the sun goes down and this should hold it at shock level. Then I test the water and let it sit over night and test in the morning to see where it is. If I hold within 1.0 then I can stop shocking and let the levels get down to acceptable range. If there is a drop overnight I keep shocking. Does this sound right?

Re: Need advice on test results and pool issue

Close...you measure the pool each time before adding more bleach/liquid chlorine and use poolcalculator.com to calculate how much more bleach/LC to put in. Do this as often as possible, with 1 hour intervals being a good shortest time between. Tonight after the sun is off the pool, measure and redose to 20 ppm FC, then after and hour of circulation, do the evening FC test (also test CC). Leave the pump running overnight, but do not add any more chlorine. In the morning before the sun hits the pool retest FC (and CC) and see how far it has dropped. If it has dropped less than 1 ppm (and your CC is less than 0.5 ppm), then it is safe to assume your pool is algae free and you can let your FC level drop back down to normal levels. If you do not pass then continue the shocking process.

Re: Need advice on test results and pool issue

Noticed calculations were wrong. If I need to bring FC to 15 to shock it then with 50 CYA readings I need to go to 373 oz of bleach so that would be 2 full bottles. I am putting the bleach in now...TA to 90 and PH right at 7.2

Re: Need advice on test results and pool issue

Went back over it again...CYA/FC chart show shock value of 20 for 50 and 16 for 40. If I go on the high end and say 20 then I put that figure into the pool calculator FC box and calculated at 12,000 gallons. That actually gave me 498 oz so I added another bottle of bleach whic equals 492oz in the pool right now. Does that sound right?

Re: Need advice on test results and pool issue

Update...Pool held the chlorine pretty well last night. Chlorine levels only fell a couple points. I had to leave this morning and just got back and tested the water. The Chlorine is still holding under the hot sun at normal ratings (FC and TC around 4). PH and TA holding at 7.2/90. I did notice that CYA went up from around 50 to around 90. I was chlorinating with tabs but the tabs have not been in the pool since I started this process. The black staining looks like it may have gone away a bit but is definately still there. I did not notice any of it turning white or clouding the pool at all. I am still wondering if maybe it isn't algae at all. CH is still at same high levels.

Re: Need advice on test results and pool issue

I had to use a test strip for CYA because I ran out of the regular test. Probably a bad reading then because all I used was Baking soda, bleach and the soda ash since I had the 50 reading to start the process.

Re: Need advice on test results and pool issue

I did do that all day yesterday. Today is the first time I tested it where the FC was in the normal range of 4-5. It held close to shock level overnight which is what pool school says is one of the signs that you can stop shocking if I understand it right. CC is 0...FC held close to 1 overnight, it was only a couple off...Water is clear, just has the black staining but it has never been cloudy. My question was how to move forward with those numbers and strange CYA reading, and also given everything what the black staining might be...I will go have the CYA tested using the better tester and then bring it back to shock level again if that is the recommendation